Tox: Combining basepython and an env with "py" in its name raises an exception

[moggers87]

If a test environment has basepython set and has "py" in the environment name, e.g. py-test, tox fails with an exception. If I install tox<3.4 or add ignore_basepython_conflict to tox.ini the exception goes away.

This appears to have been caused by 1432cfbd19bb529e9a57cef21eb4923d77a8206c as a guard against non-matching regex was removed.

tox output

$ tox -e py-test
Traceback (most recent call last):
  File "/home/moggers/.virtualenvs/env/bin/tox", line 11, in <module>
    sys.exit(cmdline())
  File "/home/moggers/.virtualenvs/env/lib/python2.7/site-packages/tox/session.py", line 41, in cmdline
    main(args)
  File "/home/moggers/.virtualenvs/env/lib/python2.7/site-packages/tox/session.py", line 46, in main
    config = prepare(args)
  File "/home/moggers/.virtualenvs/env/lib/python2.7/site-packages/tox/session.py", line 28, in prepare
    config = parseconfig(args)
  File "/home/moggers/.virtualenvs/env/lib/python2.7/site-packages/tox/config.py", line 232, in parseconfig
    ParseIni(config, config_file, content)
  File "/home/moggers/.virtualenvs/env/lib/python2.7/site-packages/tox/config.py", line 1060, in __init__
    config.envconfigs[name] = self.make_envconfig(name, section, reader._subs, config)
  File "/home/moggers/.virtualenvs/env/lib/python2.7/site-packages/tox/config.py", line 1133, in make_envconfig
    res = env_attr.postprocess(testenv_config=tc, value=res)
  File "/home/moggers/.virtualenvs/env/lib/python2.7/site-packages/tox/config.py", line 559, in basepython_default
    implied_version = tox.PYTHON.PY_FACTORS_RE.match(factor).group(2)
AttributeError: 'NoneType' object has no attribute 'group'

tox.ini:

[tox]
skipsdist=true
envlist=
    my-test
    py-test

[testenv]
whitelist_externals=ls
commands=ls
basepython=python

pip list:

$ pip list
Package    Version
---------- -------
pip        18.0   
pluggy     0.7.1  
py         1.6.0  
setuptools 40.4.3 
six        1.11.0 
toml       0.9.6  
tox        3.4.0  
virtualenv 16.0.0 
wheel      0.31.1 

[stanislavlevin]

I have the same problem.

[gaborbernat]

Will try to fix this, however note in general we don't recommend to name environments as py- unless it signals that python basepython is to be used. You can use the underscore instead of the dash if you still want to name your environments with a py section.

[jayvdb]

I believe this was fixed in v3.8.0
I cant quickly spot which of these commits fixed it.